Conference Proceedings

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Study of microstructure and corrosion effects of precipitation hardened high strength aa-7xxx aluminium alloy subjected to cryo rolling
(Indian Maritime University, Visakhapatnam, 2019) Phaneendra, Y.; Harish Kumar, K.; Niranjan Kumar, I. N.; Prasad, V. V. S.
The strength and life of an alloy is the primary parameter taken into consideration while building hulls and superstructures for marine applications. Usually AA-7xxx is widely used for these applications and hence is chosen for the present investigation. Cast AA-7xxx alloy reveals distribution of soluble intermetallic compounds in the α-aluminium matrix. In order to improve the mechanical properties and condition the microstructural features, precipitation hardening (solutionizing and ageing) treatment was carried out by varying time and temperature. Ageing treatment was carried out at 120°C varying time interval. Thermo-mechanical treatment, in particular, cold rolling and cryo rolling(-190ºC) is a unique technique to produce super high strength aluminium alloys with elongated grained structure. In order to conduct the rolling at room temperature, the alloy ingot was rolled from 6mm to 1mm with 85% reduction in thickness. Detailed microscopic analysis was done using optical and electron microscopy to understand the phase and structural evolution during ageing. Evolution of coherent precipitates and their morphology were studied using transmission electron microscope. A potentio-dynamic polarization study was performed to evaluate the corrosion behaviour of AA-7xxx series aluminium alloy processed in 3.5% NaCl solution at different conditions. The aged, cold rolled and cryo rolled alloy is found toexhibit better corrosion resistance characteristics in comparison with other alloys.
River trash cleaner.
(Indian Maritime University, Visakhapatnam, 2019) Upendra, M.; Hadassah, T.; Nagesh, Bh.; Niranjan Kumar, I. N.
With the increase in global plastic pollution in rivers/lakes which is adversely affecting the human and aquatic life. In this paper we present the design and analysis of Zero emission River Trash Cleaner (z-RTC) which is a electrically operated self-propelled floater with trash collecting arms and trash processing plant on the floater. The z-RTC collects the trash and the processing plant on the floater separates the plastic from the trash. The design and analysis of the z-RTC covers the general arrangement, stability, hydrodynamics and structural analysis. The collected plastic will be converted to lubricant oils by having an on-site pyrolysis plant. The last section of the paper discusses about the benefits and cost estimation of z-RTC.
Mechanical properties of Al-Si17Cu3.5Mg0.8 alloy fabricated by stir casting with UV and new CRSS casting process with and without T6 condition
(Indian Maritime University, Visakhapatnam, 2019) Malleswararao, N. D.; Niranjan Kumar, I. N.
Aluminum-Silicon metal matrix composites are the popular materials in the vast majority of the car and modern industries on account of their low weight, high mechanical properties, and incredible wear opposition properties. In the present study, Al-Si17Cu3.5Mg0.8 alloy is fabricated by two casting processes such as stir casting with ultrasonic vibrations (RSC) and merged-rheo-stir-squeeze (CRSS) casting with and without heat treated (T6) condition. Microstructural and material characterization was explored by advanced metallurgical microscope (AMM), SEM and EDS. Though, tensile and hardness tests were executed by Tensometer and hardness tester (Brinell). The casting process (CRSS) greatly improves the mechanical properties than rheo stir casting about 30%. The micrograph results display uniform distribution of Si-particles in CRSS cast workpieces than the regular casting. Furthermore, mechanical values revealed that the addition of heat treatment (T6) process led to the development of hardness and tensile strength.
Probabilistic and diagnostic methods to determine the multiple failure mechanisms of HPT 1st stage marine gas turbine blade
(Indian Maritime University, Visakhapatnam, 2019) Naga Bhushana Rao, A.; Niranjan Kumar, I. N.
The failure analysis of high pressure turbine (HPT) blade belonging to 30 MW gas turbine used in marine applications is presented. Before failure, the turbine blade under evaluation was operated for about 10000 hours while its service life was expected to be around 15000 hours. The gas turbine blade was made of Nickel based super alloy and was manufactured by investment casting method. An attempt has been made to analyze the causes and modes of failure of a gas turbine blade. During operation, the turbine blade is subjected to large centrifugal forces and operated at elevated temperatures in corrosive environmental attack such as oxidation, hot corrosion and sulphidation etc. The investigation includes the activities like visual inspection, determination of material composition, microscopic examination, metallurgical analysis and Mechanical analysis. Metallurgical examination was carried out to diagnose the possible causes of blade failure of micro structural damage due to blade operation at elevated temperatures. The thermal-structural finite element analysis was performed on the turbine blades using ANSYS 14.0 software. From the results it was observed that, the temperatures are below the melting point of blade material. It was also observed that the blade might have suffered both corrosion (including HTHC & LTHC) and erosion. LTHC was prominent at the root of the blade while the regions near the tip of the blade were affected by the HTHC. It is concluded that the turbine blade failure might be caused by multiple failure mechanisms such as hot corrosion & erosion and fatigue. Hot corrosion could have been reduced the thickness of the blade material and thus weaken the blade. This reduction of the blade thickness reduces the fatigue strength which ultimately led to the failure of the turbine blade.

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